Automatic lines for packaging liquid or solid products (generally but non necessarily foodstuffs) are well known, diffused, and extensively used in industry and (therefore) will not be described herein. However, in these lines, the containers (particularly for food contact packaging) must (or at least should) be washed and/or sterilized (or anyway accurately cleaned) before being filled: therefore, at the start of the packaging line, there is normally provided at least one washing step to clear the inside of containers of dust and/or other foreign matters, which may have penetrated them.
Well-known washing steps are normally able to accomplish the task wherefore they are designed and implemented but they may (or might) exceptionally fail, with harmful effects (at least in terms of commercial impact and/or image) for product packagers and vendors; as an example, one might think of a pack (of a food or non food product), inside which a purchaser/user would find a foreign body, like (for example) a mouse, a lizard and/or one or more bugs.
The jets of fluid under pressure (air and/or water), used in many well-known washing steps are not (or may not be) able to remove these foreign bodies, from the inside of a container, when they are large, or anyway as large as the mouth of the container.
To this end, the expedient of applying a seal, made of a film of extensible material, is known from the application for international patent PCT No. WO96/23702.
WO96/23702 discloses a device for sealing container openings, which permits to apply a stretch plastic film onto the openings to be sealed. Said device comprises a support, preferably flat-shaped, having at least one hole, on which is placed the stretch plastic film. Said film is held taut and adherent to the support by means of gluing, magnetic force, pressure, a counter pattern or in any other way. The device can bear marks or recognition messages, as well as a warning or an advertisement and can also be used for temporary sealing of containers.
Relating to apparati for applying the seal, WO/03478 discloses an apparatus for covering articles with a film, comprising means for relatively moving a sheet of film toward a primary surface of an article. Said sheet and said primary surface are generally parallel to one another. The article shows a secondary surface substantially perpendicular to said primary surface. The said means for moving have an extent of sufficient length to move said film towards and past said primary surface and along said secondary surface. Furthermore the apparti comprises means for circumferentially restraining said film in a plane substantially parallel to said primary surface, whereby said means for restraining causes said film to stretch as said means for relatively moving passes said primary surface.
Also document U.S. Pat. No. 3,112,587 discloses an apparatus for closing and sealing the mouth of a container. The apparatus disclosed is an apparatus for applying a sheet of heat sealable material to the mouth of a container comprising a heat sealing head, means for advancing a sheet of heat sealable material past the sealing head, means for selectively clamping the sheet of material around a central mouth spanning area, means for moving the head, the sheet material and the container relative to each other, to bring the head and the mouth of the container into engagement with opposite sides of the mouth spanning portion of the sheet whereby to heat seal the same thereto, and means for thereafter moving the head and the container in unison relative to the clamping means with the head and container in engagement with opposite sides of the sheet to separate the mouth spanning portion from the sheet. The relative motion of the clamping means, of the head and of the bottle is achieved by actively displacing each of this parts.
Document U.S. Pat. No. 4,338,767 discloses a device for removing pressure sensitive sealing tape from a container. The apparatus has a seal removal station which is positioned along a bottle conveyor line upstream of a filling operation. In the said removal station oversized adhesive seals covering the mouth of the plastic bottles and adhering to the annular edge delimiting the mouth of the bottle are lifted off each bottle and transferred to a collector bin. Vacuum pressure generated in a plenum chamber formed in a stator member is transmitted to the nonadhesive upper surface of each seal through a perforated rotor surface rotating beneath the stator. Air jet means directing fluid pressure upward against marginal portions of each seal overlapping marginal portions of each seal and guide surfaces to flatten out curled portions of the seal are utilized to assure seal lift off by virtue of fluid pressure differentials.
DE-U-296 13 476 discloses a device for unsealing bottles having crown sealings and a film covering the crown sealing and the neck of the bottle. The device having mechanical scratching means for detaching from the neck covering sheets of paper, plastic or tinfoil.